Hi all, I have a data frame that has the columns OFB1, OFB2, OFB3,... OFB10. How do I select the first 8 columns efficiently without typing each and every one of them. i.e. I want something like: a<-data.frame(initial_data$OFB1-10) #i know this is wrong, what would be the correct syntax? Thanks, Sachin [[alternative HTML version deleted]]
mydata[ , 1:8] Or let's say you only one the 4th, 6th and 8th columns mydata[ , c(4,6,8)] and so on. There are several good intro's available on the R website that will walk you through this type of thing. If you're a recovering SAS or SPSS user this paper may be of real help www.et.bs.ehu.es/~etptupaf/pub/R/RforSAS&SPSSusers.pdf John Kane Kingston ON Canada> -----Original Message----- > From: sachin.abeywardana at gmail.com > Sent: Sat, 11 Aug 2012 21:59:59 +1000 > To: r-help at r-project.org > Subject: [R] choosing multiple columns > > Hi all, > > I have a data frame that has the columns OFB1, OFB2, OFB3,... OFB10. > > How do I select the first 8 columns efficiently without typing each and > every one of them. i.e. I want something like: > > a<-data.frame(initial_data$OFB1-10) #i know this is wrong, what would be > the correct syntax? > > Thanks, > Sachin > > [[alternative HTML version deleted]] > > ______________________________________________ > R-help at r-project.org mailing list > https://stat.ethz.ch/mailman/listinfo/r-help > PLEASE do read the posting guide > http://www.R-project.org/posting-guide.html > and provide commented, minimal, self-contained, reproducible code.____________________________________________________________ FREE 3D EARTH SCREENSAVER - Watch the Earth right on your desktop!
Hi Sachin,
There are at least two ways. The safer way is to use a regular
expression to find the matching columns, like this:
a <- initial_data[grep("^OFB[0-9]+", names(initial_data))]
Alternatively, if you know that the columns you want are the first 8
you can select them by position, like this:
a <- initial_data[1:8]
Best,
Ista
On Sat, Aug 11, 2012 at 7:59 AM, Sachinthaka Abeywardana
<sachin.abeywardana at gmail.com> wrote:> Hi all,
>
> I have a data frame that has the columns OFB1, OFB2, OFB3,... OFB10.
>
> How do I select the first 8 columns efficiently without typing each and
> every one of them. i.e. I want something like:
>
> a<-data.frame(initial_data$OFB1-10) #i know this is wrong, what would be
> the correct syntax?
>
> Thanks,
> Sachin
>
> [[alternative HTML version deleted]]
>
> ______________________________________________
> R-help at r-project.org mailing list
> https://stat.ethz.ch/mailman/listinfo/r-help
> PLEASE do read the posting guide
http://www.R-project.org/posting-guide.html
> and provide commented, minimal, self-contained, reproducible code.
HI,
Try this:
dat1<-as.data.frame(matrix(rnorm(50,5),ncol=10))
colnames(dat1)<-paste0("OFB",1:10)
#to select first 8 columns - easy method
dat1[,1:8]
#2nd method
wanted<-paste0("OFB",1:8)
dat1[,colnames(dat1)%in%wanted]
#3rd method
#regular expression to select 3rd, 5th columns
dat1[grep("[[:alnum:]][c(3,5)]",colnames(dat1))]
#???? OFB3???? OFB5
#1 6.378474 7.490392
#2 5.323282 4.728561
#3 5.415081 4.661548
#4 4.000541 5.286831
#5 3.598919 6.080370
dat2<-data.frame(dat1,CFB=rnorm(5,15))
#select columns having OFB as column name
dat2[grep("OFB",colnames(dat2))]
#select 4-8 columns
dat2[grep("[4-8]",colnames(dat2))]
?# ?? OFB4???? OFB5???? OFB6???? OFB7???? OFB8
#1 4.545049 7.490392 5.441275 3.433050 4.656184
#2 5.015531 4.728561 5.429073 5.268677 5.569176
#3 5.533485 4.661548 5.586189 4.694112 5.209213
#4 6.427448 5.286831 5.521572 4.036457 5.532234
#5 5.500054 6.080370 6.259925 3.946102 4.554102
Hope this helps.
A.K.
----- Original Message -----
From: Sachinthaka Abeywardana <sachin.abeywardana at gmail.com>
To: r-help at r-project.org
Cc:
Sent: Saturday, August 11, 2012 7:59 AM
Subject: [R] choosing multiple columns
Hi all,
I have a data frame that has the columns OFB1, OFB2, OFB3,... OFB10.
How do I select the first 8 columns efficiently without typing each and
every one of them. i.e. I want something like:
a<-data.frame(initial_data$OFB1-10) #i know this is wrong, what would be
the correct syntax?
Thanks,
Sachin
??? [[alternative HTML version deleted]]
______________________________________________
R-help at r-project.org mailing list
https://stat.ethz.ch/mailman/listinfo/r-help
PLEASE do read the posting guide http://www.R-project.org/posting-guide.html
and provide commented, minimal, self-contained, reproducible code.